This application relates to medical electrodes. It relates more specifically to disposable medical electrodes which are temporarily secured to a patient's body to provide conductive contact between the patient's skin and medical monitoring equipment.
Conventionally, these electrodes employ a thin base layer of compliant material which supports an electrical contact usually in the form of a male metallic snap fastener element. The base layer also supports a pad filled with conductive gel in intimate contact with the base of the snap fastener element.
The underside of the base layer is coated with a suitable adhesive and when the base layer is adhered to the patient's skin, the gel pad is pressed against the skin with the conductive gel making good electrical contact between the skin and the snap fastener element. Electrical connection between the monitoring apparatus is then made by attaching the snap fastener element to a mating fastener element connected to the apparatus. A typical prior disposable electrode is shown, for example, in U.S. Pat. No. 3,828,766, dated Aug. 13, 1974.
While these disposable electrodes are a vast improvement over the suction cup-type electrodes used previously, they still have some drawbacks. More particularly, in many instances, as when a patient is moved from one place to another, it is necessary to make repeated connections to monitoring apparatus after the electrode has been adhered to the patient's skin. This invariably results in movement of the snap fastener element and the underlying gel pad which, in turn, disturbs and even interrupts the conductive path between the element and the patient's skin.
In other instances, such as in stress testing, the patient must move relative to the equipment while his body signs are being monitored. Consequently, the electrical lead connected to the electrode causes movement of the snap fastener element relative to the gel pad, giving rise to electrical noise which degrades the output signals from the patient's body.
Another problem with prior pregelled medical electrodes stems from the fact that many electrolyte gels contain salt that tends to corrode the snap fastener element. To avoid the drop in conductivity and electrical noise incident to such corrosion, some electrodes are provided with silver or silverplated fastener elements which increase the overall cost of the product. Another type of electrode which we are aware of incidentally avoids this problem by placing the fastener element at one end of a long insulated wire whose other end makes connection with the electrode gel pad inside a large rigid housing at the center of the electrode. However, this solution to the corrosion problem generates further difficulties. More particularly, the long wires from the different electrodes tend to become tangled so that it is hard to locate them and to properly connect the fastener element to the correct channel of the monitoring apparatus. Further, the long leads may inadvertently be pulled when disconnected from the monitoring apparatus as when the patient is moved, thereby upsetting the conductive contact between the electrode and the skin. Also, the presence of the rigid connector housing on the electrode increases the overall size and weight of the electrode and increases patient discomfort.